You can try recovery software to recover your lost files from hard drive. I have used data recovery software, which helped me to locate and recover lost data. This software supports all major audio file types like MP3, MP4, WAV, MIDI, M4b, M4A, AIFF, AIF, AIFC, RA, AMR etc. But, make sure that you have not saved or copied any new files over hard drive from where you have lost recorded audio files. First, download demo version, where you can see list of recovered data and then you can use full version to save the recovered data.